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    SubjectRe: [PATCH] Document huge memory/cache overhead of memory controller in Kconfig
    John Stoffel wrote:
    >>>>>> "Jan" == Jan Engelhardt <jengelh@computergmbh.de> writes:
    >
    > Jan> On Feb 20 2008 20:50, Balbir Singh wrote:
    >>> John Stoffel wrote:
    >>>> I know this is a pedantic comment, but why the heck is it called such
    >>>> a generic term as "Memory Controller" which doesn't give any
    >>>> indication of what it does.
    >>>>
    >>>> Shouldn't it be something like "Memory Quota Controller", or "Memory
    >>>> Limits Controller"?
    >>> It's called the memory controller since it controls the amount of
    >>> memory that a user can allocate (via limits). The generic term for
    >>> any resource manager plugged into cgroups is a controller.
    >
    > Jan> For ordinary desktop people, memory controller is what developers
    > Jan> know as MMU or sometimes even some other mysterious piece of
    > Jan> silicon inside the heavy box.
    >
    > That's what was confusing me at first. I was wondering why we needed
    > a memory controller when we already had one in Linux!
    >
    > Also, controlling a resource is more a matter of limits or quotas, not
    > controls. Well, I'll actually back off on that, since controls does
    > have a history in other industries.
    >
    > But for computers, limits is an expected and understood term, and for
    > filesystems it's quotas. So in this case, I *still* think you should
    > be using the term "Memory Quota Controller" instead. It just makes it
    > clearer to a larger audience what you mean.
    >

    Memory Quota sounds very confusing to me. Usually a quota implies limits, but in
    a true framework, one can also implement guarantees and shares.

    >>> If you look through some of the references in the document, we've
    >>> listed our plans to support other categories of memory as well.
    >>> Hence it's called a memory controller
    >>>
    >>>> Also, the Kconfig name "CGROUP_MEM_CONT" is just wrong, it should
    >>>> be "CGROUP_MEM_CONTROLLER", just spell it out so it's clear what's
    >>>> up.
    >
    >>> This has some history as well. Control groups was called containers
    >>> earlier. That way a name like CGROUP_MEM_CONT could stand for
    >>> cgroup memory container or cgroup memory controller.
    >
    > Jan> CONT is shorthand for "continue" ;-) (SIGCONT, f.ex.), ctrl or
    > Jan> ctrlr it is for controllers (comes from Solaris iirc.)
    >
    > Right, CTLR would be more regular shorthand for CONTROLLER.
    >
    > Basically, I think you're overloading a commonly used term for your
    > own uses and when it's exposed to regular users, it will cause
    > confusion.
    >

    OK, I'll queue a patch and try to explain various terms used by resource management.

    > Thanks,
    > John


    --
    Warm Regards,
    Balbir Singh
    Linux Technology Center
    IBM, ISTL


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